A chemistry demonstration of sorts was conducted by accident Sunday in an apartment in the heart of downtown Washington, and, before it was over, the building was evacuated, according to the D.C. fire department. No injuries were reported.

Around 8 p.m. the department reported in a Twitter message that it was investigating “an ammonia-like odor” in the penthouse level of a building in the 800 block of 10th Street NW.

The building was evacuated, the fire department said. It noted in the same tweet that a water leak existed in the air conditioning chiller system.

The department’s hazmat unit, which deals with potentially hazardous substances, controlled the leak, the fire department said later.

It was the leaking water that mixed with a descaling product to produce the odor, the department said.

The incident was mitigated, the department said, and residents of apartments not directly affected by the leak were being allowed to return.

The specific chemicals involved were not immediately known.